Voltage regulator



June 18, 1963 o. T. FARRY 3,094,657

VOLTAGE REGULATOR Filed July 28, 1960 5. 6 w Ii FIG. I

3,094,657 VOLTAGE REGULATOR Otis T. Farry, University City, Mo., assignor to Wagner Electric Corporation, St. Louis, M0., a corporation of Delaware Filed July 28, 1960, Ser. No. 45,937 Claims. (Cl. 323-61) The present invention relates generally to the voltage regulator art and more particularly to a novel voltage control device by which the output voltage of a supply system such as a transformer can be held constant or can be varied in any desired manner regardless of variations of the supply voltage thereto or of the load, and which regu-latesor controls said output voltage smoothly and practically instantaneously with the demand therefor.

At the present time, the output voltage of a supply system is usually controlled or regulated by means of tap changing devices associated system by varying the impedance of a device connected in one of the supply leads or load leads of the system.

The known tap changers have the disadvantage that they require numerous switches which are subject to areing and other forms of Wear and tear, and they require relatively complicated mechanical control mechanism for their operation. Tap changers also produce stepped or incremental regulation and produce abrupt changes or interruptions in the circuit connections. Furthermore, the best available regulation employing tap changers is relatively poor, producing error of the order of of 1% of normal voltage. Also, tap changers are relatively slow acting, being effective only after the output voltage has been at an abnormal value for an appreciable period of time.

In the past, saturable reactors have also been employed, to regulate the output voltage of a supply system. However, reactors present relatively high impedance to current flow even when the supply voltage is normal and this. introduces. considerable undesirable phase shift in the system.

Therefore it isv one of the main objects of the present invention to provide a novel voltage-control device for useinia supply system whereby the output voltage of the system can be changed to any desired value or maintained substantially constant regardless of changes in the supply voltage or loadwithin predetermined-limits.

More particularly, it is an object to provide such a device in which load voltage can be maintained substantially constant within very narrow limits when the supply or load voltage varies fromits normal value.-

Another object of the present invention is to provide a voltagecontrol device for regulating the output voltageof. a supply system without interrupting the normal flow of power.

Another object is to provide such a device whereby the control voltage is varied smoothly, as. distinguished from stepwise or increment variations, and in which the corrective changes take place substantially instantaneously.

Another objectis to minimize the repair and maintenance costs of a voltage regulator.

Another object. is to provide relatively inexpensive with a winding of the supply.

means involving a minimum number of movable parts for. controlling. or regulating the output voltage of an alternating current-system or device.

Another object is to provide a voltage control device employing saturable reactors which introduces a minimum of phase shift in the system being controlled.

Yet another object is to provide substantially instantaneous acting meansfor accurately controlling the output of an alternatingcurrent device.

3,094,657. Patented June 18, 1963 2 1 These and other objects and advantages of the present invention will be readily apparent atter considering the following detailed description of one embodiment of the invention in conjunction with the accompanying drawmg.

In the drawing:

FIG. 1 is a schematic wiring diagram showing for illustrative purposes a transformer, circuit equipped with voltage regulatingmeans constructed according to the present invention; and V FIG. 2 is a typical graph showing variationsin the reactances of reactors 12, 13 and 14 of FIG. 1 plotted as a function of input voltage.

In FIG. 1, a transformer 1 is shown connected across a source of alternating current 2 and across a load 3. The primaryside of the transformer 1 has three windings which are shown as windings 4, 5 and 6. Thewinding 4 has an end tap 7 opposite its connection to the source 2, the winding Shasthree-taps 8, 9 and 10 as shown, and the winding 6' has a tap 11 which is opposite its connection to the source 2. The tap 11 on winding 6 is connected to the taplt) on winding S. The taps 7 and 11 are on; the ends of windingsfland 6- respectively nearest the center or COI'IGCtQI winding S, and the taps 8 and 10 are onopposite endsof the winding 5. The tap 9 is at an intermediate position on the winding 5.

Three saturable reactors 12,- 13 and 14 are connected to the taps on Each of the. saturable reactors v12, 13 and 14 has an alternating current reactance winding and a direct current control winding. The alternatin -current windings ofthe reactors 12, 13- and 14, are windings 15,16 and 17 respectively, and the direct current windings are windings 18,- 19 and 20 respectively.

The alternating current winding 15 of the reactor 12 is connected between the taps 7 and 8, thealternating cur rent winding 16;.of thereactor 131s connected between.

the taps 7 and 9, and thealternating current winding.

of the reactor 14- is connected between the taps 7 and 10.

Three separatesources ofdirect current, shown as;

batteries 21", 22 and 23 and associated rheost-ats 24, 25 and 26 are connected respectively across the directcurrent ings 18, 19 and 20 ofthe saturable reactors 12,113'and 14 can be varied, and this in-turnadjusts the reactancesof the associated alternating current windings 15, 16 and 17 ina manner well known. By varying the reactances of.

the reactors 12, 13 and 14 in a desired way, it is possible to maintainthe output voltage of the transformer 1 constant or at a particular desired value regardless of variations in the load voltage or supply voltage as willv be shown;

When the supplyvoltage is normal, the primary windings 4, 5 and 6 of thetransformer 1' must have a certain predetermined total number of efiective turns in order to maintain a ratio oftransformation between primary and secondary that will. produce normal output voltage across theload 3. The combined number of turns in both of the primary windings 1 4Iand 6 is therefore arbitrarily chosen to be equal to' somewhat less than the total number of primary turns necessary toproduce normal output when theinput voltage isnormal. For example, if each of the primary windings 4 and 6 is constructed to have.

the aforementioned transformer windings. p

24, 2s} and 26,

have an additional 20% of the necessary number of primary turns, then if the tap 9 is positioned in the middle of the winding it is possible to control the output voltage and maintain the output voltage constant over a range of variation of supply voltage (or load voltage) of i% of normal. In this example, when normal supply voltage is across the primary and normal load voltage is across the load 3, the react-ances of the alternating current windings and 17 of the reactors 12 and 14 respectively are adjusted to be relatively high, and the reactance of the alternating current Winding 16 of the reactor 13 is adjusted to be relatively low. In this situation the part of the corrector winding 5 between the taps 9 and 10 is connected in series with the low impedance of the reactor winding 16 and also in series with the windings 4 and 6; and the part of the winding 5 between the taps 8 and 9 is practically ineffective because it is connected in series with the high reactance of the alternating current winding 15. Therefore, the number of effective primary turns of the transformer assuming all the windings are wound so as to aid, is 100% of the turns necessary to produce normal output voltage. This is the normal condition of the circuit.

When, however, the supply voltage rises above the normal value, the reactance of the alternating current winding 15 of the reactor 12 is readjusted to have a relatively low value, and the reactance of the windings 1'6 and 17 of the reactors 13 and 14 respectively are adjusted to be relatively high. This is done to change the ratio of transformation so that the output voltage will remain normal. If for example, the supply voltage rises to 110% of normal, then to maintain the output voltage normal it is necessary to adjust the reactance of the alternating current windings 16 and 17 of the reactors l3 and 14 to have very high reactances and to adjust the reactance of the alternating current winding 15 to a relatively low reactance approaching a short circuit. This has the effect of shorting between the taps 7 and 8 whereby substantially all of the current flows through windings 4 and 6 and also flows through winding 5. Thus the turns on the primary side of the transformer 1 are increased to approximately 110% of normal thereby increasing the transformer turns ratio, which is the ratio of the turns of the primary winding divided by the turns of secondary winding 27 to maintain normal output voltage. The turns ratio is expressed in equation form as:

When, however, the input voltage drops below normal, the reactance of the winding 17 is adjusted to be relatively low and the reactances of the windings 15 and 16 are adjusted to be relatively high. If the supply voltage drop is to 90% of normal, the number of turns in the primary has to be reduced to 90% of normal to maintain normal output voltage. In this situation and with the adjustments described, namely, the high reactances of the windings 15 and 16 and the low reactance of the winding 17, no appreciable current flow-s through any part of winding 5 because the winding 5 is substantially shorted. Therefore, substantially all of the current flowing in windings 4 and 6 is shunted around winding 5 by means of the low reactance of the Winding 17. Therefore, the primary turns of the transformer 1 are decreased to 90% or normal to maintain the output voltage normal. It is thus possible to maintain the output voltage constant or normal while the input voltage varies from normal between the extremes of 90% and 110% of normal, and even this range can be changed by selecting different components.

In the above explanation the three simplest cases are considered and in each case only one of the three saturable reactors 12, 13 and 14 is adjusted to have a low reactance. It is also to be noted in the above examples that in each case the reactance of two of the reactors is adjusted to be relatively high. Furthermore, in the above examples, only the cases of the supply voltage being normal or of the supply voltage being at an extreme condition of 110% or 90% of normal are considered.

It is also possible to adjust the reactors to compensate for changes in supply or load voltages at any point between these extremes by using intermediate settings for the reactors. For example, for supply voltages that decrease from 110% of normal to normal it is to be understood that the reactance of the winding 15 is to be increased substantially from a minimum to a relatively high .value while the reactance of the winding 16 is decreased from maximum to a minimum reactance. In like manner, to regulate for values of the supply voltage between 90% of normal and normal the reactances of the windings 16 and 17 are varied while the reactance of the winding 15 is held substantially constant at a high value. Also for supply voltages that increase from 90% of normal to normal the reactance of the winding 17 is increased from a low to a high value while the reactance of the winding 16 is decreased from a high to a low value.

Thus for all values of input voltage within the range of the control it is possible to adjust the reactors so that the output is maintained normal or at any other desired value.

In FIG. 2 is shown a graph of the relative changes in the values of the reactances of the reactors 12, 13 and 14 plotted as a function of input voltage. The changes shown in the graph are for illustrative purposes only and do not necessarily represent actual values of reactances.

It is seen in FIG. 2 that the reactance of winding 17 is at a low value when the supply voltage is 90% of its normal value; reactance of winding 16 is at a low value when the supply voltage is at its normal value; and reactance of Winding 15 is at a low value when the supply voltage is at 110% of its normal value. Thus, the reactance of one of the three reactance windings is at low value when the supply voltage is at 90%, 100% and 110% of its normal value. This means that the average reactance voltage drop due to the reactors in the system are relatively low over the control range and that therefore the VARs (volt-ampere-reactive units) required by the control system are relatively low. Also, because the reactance of one of the reactance windings is at a low value when the supply voltage is at its normal value (Winding 16) as well as when the supply voltage is 110% and 90% of its normal value (windings 15 and 17), the effective reactance in the system due to the reactors is relatively low, thus substantially avoiding any phase shift between the supply and output voltages of the system.

It is to be understood also that the above examples of regulation also apply in the situations where the load varies and the source remains relatively constant. In such situations the same general principles apply.

It is now apparent that there has been shown and described a voltage regulator device which fulfills all of the objects and advantages sought therefor. The device may be employed on a transformer although it has broad uses on many types of alternating current controlled systems, said device comprising a plurality of variable impedance devices connected across different selected portions of the controlled systems, and means for varying the impedances of said devices for changing the effectiveness of various components of said system to thereby regulate the output therefrom.

Various changes, modifications and alterations of the present device will become apparent to those skilled in the art after considering this specification and the accompanying drawing. All such changes, modifications and alterations which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.

What is claimed is:

1. Voltage control means comprising a transformer winding having end taps and an intermediate tap, means for "coupling said winding to a voltagesupply source, first, second and third reactors each having one endconnected together, the other ends of said reactors being respectively connected to different ones of said taps, and means for varying the reactance of said reactors for providing a variable voltagebetween said connected together ends of said reactorsand one of said taps.

2. In a supply system having a power output circuit connectable to a load and .a power input circuit connectable to a power supply source for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit within predetermined limits, said control means being coupled in series circuit relation between said power input and output circuits and comprising a transformer winding having end taps and a center tap, first, second and third reactors each having one end connected together, the other ends of said reactors being respectively connected to different ones of said winding taps, and means for varying the reactance of said reactors.

3. Voltage regulator means for a transformer having a primary winding for connection to an alternating current source and a secondary winding for connection to a load, comprising a corrector winding, and three reactive circuits each including a saturable reactor having a direct current winding for varying the impedance thereof, one of said reactive circuits being connected in series with the corrector winding and one of the other of said windings, a second of said circuits being connected to by-pass said corrector winding, and a third of said circuits being connected in series with part of said corrector winding.

4. In a supply system having a power output circuit for connection with a load and a power input circuit for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit, said control means comprising a first circuit including a first reactor and a transformer winding connected in series with one another in one of said power circuits, a second circuit including a second reactor connected in parallel circuit relation with said first reactor and a portion of said winding, a third circuit including a third reactor connected in parallel circuit relation with said first circuit, and means for varying the reactance of said reactors.

S. In a supply system having a power output circuit for connection with a load and a power input circuit for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit, said control means comprising a series circuit including a first reactor and a transformer winding coupled in series circuit relation between said power input and output circuits, a second reactor connected in parallel circuit relation with said first reactor and in series circuit relation with a portion of said winding, a third reactor connected in parallel circuit relation with said series circuit, and reactor control means for varying the reactance of said reactors.

6. In a supply system having a power output circuit for connection with a load and a power input circuit for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit, said volt-age control means comprising a first circuit including a first saturable reactor and a corrector winding connected in series circuit relation, means coupling said first circuit in series circuit relation between said power input and out put circuits, a second circuit including a second saturable reactor connected in parallel circuit relation with said first reactor and a portion of said winding and in series with another portion of said winding, a third circuit including a third saturable reactor connected in by-passing relation with said winding, and reactor control means for varying the reactance of said reactors.

7. In a supply system having a power output circuit for connection with a load .andra. power input circuit for supplying power to thepower output circuit, the combination therewith of voltage control means for controlling said main winding, and said corrector winding connected in series circuit relation with one another across one of said power circuits, a second circuit including a second saturable reactor connected in parallel circuit relation with said firs-t reactor and a first portion of said corrector winding and in series circuit relation with said main winding and a second portion of said corrector winding, a third circuit including a third saturable reactor connected in byapassi-ng relation with said first and second reactors and said cor-rector winding, and reactor control means for varying the reactance of said reactors.

8. In a supply system having a power output circuit for connection with a load and an alternating current source for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit comprising a transformer having a main winding and a corrector winding, a first circuit including a first saturable reactor, said rnain winding, and said corrector winding connected in series with one another across said source, a second circuit including a second saturable reactor connected in parallel circuit relation with said first reactor and a first portion of said corrector winding, and in series with said main winding and a second portion of said corrector winding, a third circuit including a third saturable reactor connected in series with said main winding and in lay-passing relation with said first and second reactors and said corrector winding, and reactor control means for varying the reactance of said reactors.

9. In -a supply system having a power output circuit for connection with a load and a power input circuit for supplying power to the power output circuit, the combination therewith of voltage control means for con trolling the voltage supplied to the power output circuit, said control means comprising, first second, and third saturable reactors each having an alternating current winding and a control winding, a corrector winding, the alternating current winding of said first reactor being connected in series with said corrector winding in one of said power circuits, the alternating current winding of said second reactor being connected in parallel circuit relation with the alternating current winding of said first reactor and a first portion of said corrector winding, and in series relation with another portion of said corrector winding, the alternating current winding of said third reactor being connected in parallel circuit relation with the alternating current windings of said first and second reactors and both of said portions of said corrector winding, and means for supplying current to the control windings of said reactors for controlling the reactance of said alternating current windings.

10. In a supply system having a power output circuit for connection with a load and a power input circuit for supplying power to the power output circuit, the combination therewith of voltage control means for controlling the voltage supplied to the power output circuit, said control means comprising a transformer having main primary and secondary windings and a corrector winding, first, second, and third saturable reactors each having an alternating current winding and a control winding, a first circuit including said corrector winding, the alternating curret winding of said first reactor, and one of said main windings connected in series with one another across one of said power circuits, the other of said main windings being connected in circuit across the other of said power circuits, a second circuit including the alternating current winding of said second reactor connected in parallel circuit relation with the alternating current winding of said first reactor and a first portion of said corrector winding,

'3" t and in series relation with a second portion of said corrector Winding and said one main winding, a third circuit including the alternating current winding of said third reactor connected in parallel circuit relation with the alternating current windings of said first and second reac- 5 tors and said first and second portions of said corrector winding, and in series relation with said one main winding, and means fior supplying current to the control windings of said reactors for controlling the reactance of said alternating current windings.

References Cited in the file of this patent 

4. IN A SUPPLY SYSTEM HAVING A POWER OUTPUT CIRCUIT FOR CONNECTION WITH A LOAD AND A POWER INPUT CIRCUIT FOR SUPPLYING POWER TO THE POWER OUTPUT CIRCUIT, THE COMBINATION THEREWITH OF VOLTAGE CONTROL MEANS FOR CONTROLLING THE VOLTAGE SUPPLIED TO THE POWER OUTPUT CIRCUIT, SAID CONTROL MEANS COMPRISING A FIRST CIRCUIT INCLUDING A FIRST REACTOR AND A TRANSFORMER WINDING CONNECTED IN SERIES WITH ONE ANOTHER IN ONE OF SAID POWER CIRCUITS, A SECOND CIRCUIT INCLUDING A SECOND REACTOR CONNECTED IN PARALLEL CIRCUIT RELATION WITH SAID FIRST REACTOR AND A PORTION OF SAID WINDING, A THIRD CIRCUIT INCLUDING A THIRD REACTOR CONNECTED IN PARALLEL CIRCUIT RELATION WITH SAID FIRST CIRCUIT, AND MEANS FOR VARYING THE REACTANCE OF SAID REACTORS. 